Methods for forming a sensor array package

ABSTRACT

Various methods for forming a low profile assembly are described. The low profile assembly may include an integrated circuit. The integrated circuit as well as components associated with the integrated circuit may be positioned below a surface plane of a printed circuit board in which the integrated circuit is located. The integrated circuit may include bond wires configured to electrically connect the integrated circuits to other components. The low profile assembly may include forming various layers over a substrate and later removing some of the layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/252,596, filed Apr. 14, 2014, entitled “METHODS FOR FORMING A SENSORARRAY PACKAGE”, which is a divisional of U.S. application Ser. No.13/632,145, filed Sep. 30, 2012, entitled “SENSOR ARRAY PACKAGE”, nowU.S. Pat. No. 8,736,080, which claims the benefit of U.S. ProvisionalPatent Application No. 61/640,589, filed Apr. 30, 2012, entitled “SENSORARRAY PACKAGE”, the contents of which are incorporated herein byreference in their entirety for all purposes.

FIELD

The described embodiments relate generally to packaging for sensors, andmore particularly, to low profile sensor array packages.

BACKGROUND

Sensors and sensor arrays can be formed from customized integratedcircuits. Sensor arrays are often used to sense environmentalcharacteristics or can act as a user input for computing devices. Sensorarrays are often formed on a silicon wafer, using similar processingtechniques to those used to fabricate other integrated circuits, such asmemories, processors, field programmable gate arrays (FPGAs) and thelike.

Sensors, unlike some general purpose integrated circuits, can haveunique packaging and mounting requirements. Typical integrated circuits,for example, can have related silicon bonded out, and then packaged. Thebonding out steps can couple signals on the silicon to pins or balls onthe package. The packaging step can include encapsulating the silicondie in a package (typically plastic or ceramic). The packing can supportand protect the otherwise fragile silicon die. However, since sensorsare meant to interface with the environment, the packaging steps areoften different.

Sensors are often outward facing, and generally exposed to a userenvironment. Instead of having the silicon die protected by a package,the die is often times exposed on the surface of a supporting element.While such configurations permit the sensor to function, theseconfigurations can be bulky and can take up a relatively large amount ofvolume, increasing the size of a user device in which the sensor isultimately used.

Therefore, what is needed is a sensor, sensors, and/or sensor arrayswhich overcome these and other drawbacks.

SUMMARY

One embodiment of a low profile sensor array assembly can include asensor disposed on a first side of a substrate. Signal trenches can alsobe formed on the first side of the substrate and can be near sensorsignal pads and extend to one edge of the substrate. A conductive layercan be deposited in the signal trench and couple to sensor signal pads.Bond wires can attach to the conductive layer and can couple signalsfrom the sensor to external pads.

Another embodiment of a low profile sensor array assembly can include asensor disposed on a first side of a substrate. The substrate caninclude a shaped feature on a first edge positioned near a signal pad ofthe sensor. The shaped feature can be configured to support a wire bondball below a surface plane relative to the sensor. A conductive layercan be deposited on the substrate coupling the signal pad and the wirebond ball. A bond wire can be coupled to the wire bond ball and bearranged to remain below the surface plane relative to the sensor.

According to another embodiment of the invention, a low profileintegrated circuit assembly includes at least one integrated circuit, asubstrate including a first side, wherein the integrated circuit isdisposed on the first side, at least one signal trench, formed on thefirst side of the substrate, proximate to an integrated circuit signalpad and extending to one edge of the substrate, a conductive layerdisposed in the signal trench and coupling to the integrated circuitsignal pad, and a bond wire configured to couple the conductive layer toan external pad wherein the bond wire, signal trench and conductivelayer are maintained below a surface plane of the integrated circuit.

According to another embodiment of the invention, a low profile circuitassembly includes an integrated circuit, a substrate including a firstside, wherein the integrated circuit is disposed on the first side, ashaped feature on a first edge of the substrate disposed proximate to anintegrated circuit signal pad and arranged to support a wire bond ballbelow a surface plane of the integrated circuit, a conductive layerdisposed on the first side of the substrate and configured to couple theintegrated circuit signal pad to the wire bond ball, and a bond wirecoupled to the wire bond ball and configured to remain below the surfaceplane of the integrated circuit.

According to another embodiment of the invention, a low profile assemblyincludes a first substrate, a second substrate, larger than the firstsubstrate, wherein the first substrate is disposed on a first side ofthe second substrate, and at least one signal trench disposed on thefirst side of the second substrate and configured to support bond wireconnections to the first substrate below a surface plane of the firstsubstrate.

According to another embodiment of the invention, a method of forming alow profile assembly includes forming at least one signal trench in asubstrate, depositing a barrier layer over the substrate proximate theat least one signal trench, depositing a seed layer of metal in the atleast one signal trench, masking the substrate, barrier layer, and atleast one signal trench, depositing additional metal over the maskedsubstrate, and removing the mask and seed layer to form a finalconductive layer in the at least one signal trench.

Other aspects and advantages of the invention will become apparent fromthe following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the described embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings. These drawings in no waylimit any changes in form and detail that may be made to the describedembodiments by one skilled in the art without departing from the spiritand scope of the described embodiments.

FIGS. 1A and 1B are simplified diagrams of a low profile sensor, inaccordance with one embodiment.

FIGS. 2A-2D illustrate side views of exemplary embodiments of a lowprofile sensor.

FIGS. 3A-3D illustrate possible shape profiles for signal trenches.

FIGS. 4A-4G illustrate steps that can be used to form a signal trench.

FIG. 5 is a flow chart of method steps for forming signal trenches in asubstrate.

FIG. 6 is a side view of signal trench, in accordance with oneembodiment of the specification.

FIG. 7 shows another embodiment of a low profile sensor.

FIG. 8 shows a side view of one embodiment of a way of forming multiplelow profile sensors.

FIG. 9 illustrates optional features that can be applied to a lowprofile sensor assembly embedded in a PCB.

FIGS. 10A and 10B illustrate another embodiment of a low profile sensor.

FIGS. 11A-11E illustrate steps that can be used to mount a low profilesensor on a substrate.

FIG. 12 is a flow chart of method steps for mounting a low profilesensor on a substrate.

FIG. 13 is a top view of yet another embodiment of a low profile sensor.

DETAILED DESCRIPTION

Representative applications of methods and apparatus according to thepresent application are described in this section. These examples arebeing provided solely to add context and aid in the understanding of thedescribed embodiments. It will thus be apparent to one skilled in theart that the described embodiments may be practiced without some or allof these specific details. In other instances, well known process stepshave not been described in detail in order to avoid unnecessarilyobscuring the described embodiments. Other applications are possible,such that the following examples should not be taken as limiting.

In the following detailed description, references are made to theaccompanying drawings, which form a part of the description and in whichare shown, by way of illustration, specific embodiments in accordancewith the described embodiments. Although these embodiments are describedin sufficient detail to enable one skilled in the art to practice thedescribed embodiments, it is understood that these examples are notlimiting; such that other embodiments may be used, and changes may bemade without departing from the spirit and scope of the describedembodiments.

Sensors and sensor arrays are often fabricated on a silicon die and thensupported with a structure underneath the die. To protect the surface ofthe sensor, often a clear cover is applied. However, some embodimentsrequire little if any cover over the sensor, to increase sensorsensitivity. Furthermore, the support structure can be bulky and in turnincrease the size of a product design including the sensor.

One embodiment of a low profile sensor can include a sensor disposed ona silicon die. The silicon die, in turn, can be embedded in a printedcircuit board (PCB) structure. The low profile sensor can include signaltrenches formed in the silicon to allow bond wires to couple to thesensor, while remaining substantially below a surface plane of thesensor. Bond wires can couple the sensor directly to other embeddeddevices, or to one or more conductive layers in the PCB.

Signal trenches can be formed by removing substrate material such aswith a saw or grinder, or signal trenches can be formed by selectivelyetching the substrate. After forming the signal trench, a conductivematerial can be deposited into the trench forming a conductive pathbetween a sensor pad and the trench. Finally, a bond wire can beattached to the conductive material and can be used to couple signalsfrom the sensor to external devices or other components.

FIGS. 1A and 1B are simplified diagrams of a low profile sensor 100, inaccordance with one embodiment of the specification. FIG. 1A shows a topview of the low profile sensor 100. Low profile sensor 100 can include asubstrate 102 and a sensor 104 disposed on a first surface of substrate102. Substrate 102 can be silicon or any other technically feasiblematerial such as gallium arsenide, gallium nitride or the like. Sensor104 can be a single sensor or an array of sensors. Sensor 104 can beused to detect user input such a touch (pressure), heat or capacitivesensor. In other embodiments, sensor 104 can be any other feasibleintegrated circuit. Such integrated circuits can be formed on anytechnically feasible substrate such as silicon, gallium arsenide or thelike. In other words, the mounting techniques described herein can beapplied equally to any integrated circuit, not only sensors. Throughoutthis specification, reference will be made to a sensor in thedescription, but it is understood that any integrated circuit can besubstituted for the sensor. Also disposed on the first surface are pads106 that can be electrically coupled to signals in sensor 104. FIG. 1Aalso shows a top view of a signal trench 108. A layer of metal 110 (orother conductor) can be deposited in signal trench 108 and couple to pad106. This is described in greater detail below in conjunction with FIG.4. FIG. 1B is a side view of low profile sensor 100. This view showssome detail of a possible shape of signal trench 108 within substrate102. The shape of the signal trench 108 is indicated with dashed lines.

FIGS. 2A-2D illustrate side views of exemplary embodiments of a lowprofile sensor. FIGS. 2A and 2B shown low profile sensor 100 embedded ina PCB. FIGS. 2C and 2D show low profile sensor 100 mounted on thinsubstrate, such as a flex circuit. These figures are not drawn to scale,but are meant to show relationships between low profile sensor 100 andPCB or low profile sensor 100 and thin substrate. These figures are notmeant to be exhaustive and show every possible configuration, but ratherillustrate exemplary approaches. Persons skilled in the art canappreciate that other approaches exist. FIG. 2A illustrates a firstbonding approach 200 between substrate 102 and PCB 204. Substrate 102can include a sensor 104 disposed on a first side. Signal trenches 215are shown in side view. Metal layer 110 can be formed in signal trenches215 and can couple to pad 106. Bond wire 208 can couple metal layer 110to a pad 210 that can be on any layer within PCB 204. Bond wire 208 canbe implemented to be below the surface plane 220 of sensor 104. Asurface plane can be an imaginary plane that extends in all directionsand is co-planar with the highest surface of sensor 104. Surface plane220 is denoted with a dashed line.

FIG. 2B illustrates a second bonding approach 250 between substrate 102and PCB 204. Sensor 104 is mounted on substrate 102 and includes pad106. Signal trenches 215 can be formed in substrate 102 and can includemetal layer 110 coupled to pad 106. Substrate 102 and separate device252 can be embedded together in PCB 204. In some embodiments, two ormore separate devices 252 can be embedded in PCB 204. Device 252 can bea separate integrated circuit that can be used to provide additionalfunctionality to sensor 104. For example, device 252 can be a signalprocessing device used to preprocess signals from sensor 104. Device 252can include at least one pad 254 to couple to signals within device 252.Bond wire 208 can couple metal layer 110 to device 252. Bond wire can bemaintained below surface plane 220.

FIG. 2C illustrates a third bonding approach 260 between substrate 102and thin substrate 225. In one embodiment, thin substrate 225 can be aflexible circuit (flex circuit). Substrate 102 can be affixed to thinsubstrate 225 with an adhesive, such as a glue, epoxy or tape adhesive.Sensor 104 can be disposed on substrate 102. Signal trenches 215 can beformed on substrate 102 and can support metal layer 110 over pad 106. Abond wire 208 can couple metal layer 110 to a pad 210. In thisembodiment, bond wire 208 can be maintained below surface plane 220.

FIG. 2D illustrates a fourth bonding approach 270 between multiplesubstrates and thin substrate 225. As shown, a first substrate 102A anda second substrate 102B are affixed to thin substrate 225. Bond wire 208can be used to couple metal layers 110 from two or more substrates. InFIG. 2D, bond wire 208 can couple signals from first substrate 102A tosecond substrate 102B. In this manner, two or more substrates 102A, 102Bcan be linked together.

FIGS. 3A-3D illustrate possible shape profiles for signal trench 215. Inone embodiment, the shape profile of the signal trench can affect signalintegrity of the signals carried within the signal trenches 215. Forexample, some common metal deposition techniques (i.e., filamentevaporation or electron beam evaporation) can have poor coverage onvertical or near vertical surfaces Other metal deposition techniques canhave improved coverage on vertical or near vertical surfaces, but mayhave other associated costs (i.e., sputter deposition). In other words,certain shape profiles can be preferred over others depending on aselected metal deposition method. Other shape profiles can be possiblebeyond the exemplary shapes described below.

FIG. 3A illustrates a vertical profile 301 for signal trench 215. Thevertical profile 301 can be formed by many methods, including saw bladeand deep reactive ion etch techniques. In some embodiments, two or moreshaping methods can be combined to create vertical profile 301. Asshown, vertical profile 301 can include at least one substantiallyvertical section 302. In some embodiments, vertical or near verticalsections may not have relatively even metal coverage. An uneven metallayer can include voids or other irregularities that could result in adiscontinuity in the metal.

FIG. 3B illustrates a ramp profile 303 for signal trench 215. The rampprofile 303 can be formed a number of ways. In one embodiment a sawblade can be used to form and shape signal trench 215. In anotherembodiment, ramp profile 303 can be formed, at least in part, by wetetching with potassium hydroxide (KOH). Etching with potassium hydroxidecan have the advantage that, by virtue of the reactant, a ramp angle isnaturally produced. One advantage of ramp profile 303 is that theprofile includes no substantially vertical portions. Thus, the shape ofthe profile can enable the deposition of relatively even metal layers110.

FIG. 3C illustrates an engineered curve profile 305 for signal trench215. Engineered curve profile 305 can be formed with a shaped saw blade,or by etching. In some embodiments, two or more shaping methods can becombined to create engineered curve profile 305. One advantage ofengineered curve profile 305 is that the profile does not include anysharp bends or curves. Sharp bends or curves can become stress pointswithin the substrate 102. These stress points can become starting pointsfor fractures and cracks. Another advantage of engineered curve profile305 is that the profile does not include any substantially verticalportions, therefore the profile can support the formation of relativelyeven metal layers.

FIG. 3D illustrates a bowl shaped profile 307 for signal trench 215.This profile can be formed with a saw or with etching methods. Oneadvantage of the bowl shaped profile 307 is the inherent strength of theprofile. Substrate area near bowl shaped profile 307 can be relativelystronger when compared to areas near other profiles such as ramp profile303. A drawback of the bowl shaped profile 307 it that it can include arelatively vertical region 308. As described above, vertical regions candevelop discontinuities and voids when certain metal depositiontechniques are used.

FIGS. 4A-4G illustrate steps that can be used to form signal trench.These illustrations are cross sectional views of the trench, with thesurrounding areas not drawn to clarify the drawing. FIG. 4A shows apossible beginning state including substrate 102. Pad 106 and sensor 104are disposed on a first side of substrate 102. FIG. 4B shows substrate102 with signal trench 215 formed into the substrate 102. Sensor 104 andpad 106 remain on the surface of substrate 102. Signal trench 215 can beformed in the shape of any technically feasible profile. Exemplaryprofiles are described above in FIGS. 3A-3D. A ramp profile (shown inFIG. 3B) is selected as the exemplary profile in this figure. A rampprofile can be formed using a potassium hydroxide etch process, forexample. FIG. 4C shows a barrier layer 405 deposited on the substrate102. In one embodiment, barrier layer 405 can be formed with techniquessimilar to forming passivation layers. In one embodiment, barrier layer405 can help protect sensor 104.

FIG. 4D shows substrate 102, pad 106 and sensor 104. In this view, ametal seed layer 410 has been deposited over the substrate 102, barrierlayer 405 and pad 106. As shown, metal seed layer 410 can be depositedin the regions of the signal trench 215 where a final conductive channelis desired. In one embodiment, metal seed layer 410 can be deposited bysputtering a conductive metal, such as aluminum. FIG. 4E shows substrate102, pad 106 and sensor 104 with a mask 415 selectively applied to thefirst surface. Mask 415 can be used to define regions where additionalmetal can be deposited over the metal seed layer 410. In one embodimentmask 415 can be a liquid photoimageable mask. FIG. 4F shows metal layer420 deposited over substrate 102, pad 106, metal seed layer 410 and mask415. During the metal deposition process, metal can be non-selectivelydeposited over the entire substrate 102. In FIG. 4G shows substrate 102after the mask 415 and excess metal seed layer 410 is removed. In oneembodiment, metal seed layer 410 can be removed with a wet etch process.Removal of the mask 415 and metal seed layer 410 can define the finalshape of the metal layer 420 in signal trench 215.

FIG. 5 is a flow chart 500 of method steps for forming signal trenchesin a substrate. The method begins in step 502 where the trench profileis formed in the substrate. The trench profile can be selected from oneof the profiles described in FIGS. 3A-3D, or any other technicallyfeasible profile. In step 504, a barrier layer can be formed anddeposited over the substrate. The barrier layer can help protect thesubstrate after trenches are formed in substrate. In step 506, a seedlayer of metal can be deposited in the formed trench and can couple tothe pad. In step 508, a mask can be selectively placed on the substrate.In one embodiment, the mask can be a liquid photoimageable mask. Themask can be used to determine the areas on the substrate where the metalwithin the signal trench will be positioned. In step 510, additionalmetal can be deposited over the substrate. In one embodiment, metal canbe sputtered. In step 512, the mask and excess seed layer can beremoved, forming the final conductive layer in the signal trench and themethod ends.

Formation of the signal trenches can provide access to signals fromsensor while maintaining connections below the surface plane of sensor104. In order to fan out the signals to other devices, wires can bebonded to the metal deposited in the signal trenches. After a wire isbonded, the wire can be routed to a pad or other conductor. Care can betaken to maintain the path of the wire to be below the surface plane ofsensor, thereby allowing a low profile mounting of the sensor andsubstrate. In one embodiment, a bond wire 208 can be formed bydepositing a wire bond ball in the signal trench on metal layer. Thebond wire can be guided within the signal trench.

FIG. 6 is a side view 600 of signal trench 215, in accordance with oneembodiment of the specification. The side view 600 includes substrate102, pad 106 and metal layer 110. Depth 602 of signal trench 215 can bea function of the elements that can be included within signal trench215. Wire bond ball 604 can be bonded to metal layer 110 in the bottomof signal trench 215. The height 606 of wire bond ball 604 can vary.Common heights can range from 5-15 μm. Diameter 608 of wire can vary byapplication; current carrying wires (power) can be thicker than wiresonly carrying signals. A typical wire diameter 608 can be 25 μm.Finally, bend radius 610 can affect the depth 602. In one embodimentdepth 602 can be determined, at least in part by the sum of the height606 plus wire diameter 608 plus bend radius 610.

The width 612 of the bottom of signal trench 215 can be determined, atleast in part, by elements that are included in the bottom of the signaltrench 215. A typical diameter 615 of wire bond ball 604 can be 50 μm.The distance 617 from the wire bond ball to the edge of the substrate102 can be 20 μm. This distance can be reduced, however, since edgechipping can occur, yield of the device can be reduced if the distanceis reduced too much. The distance 618 from the wire bond ball to theinside edge of the bottom of signal trench 15 can be between 5 to 10 μm.In some embodiments, the distance 618 can be influenced by a tool usedfor wire bonding. Thus, in one embodiment, width 612 can be determined,at least in part, by the sum of wire bond ball diameter 615, plusdistance to substrate edge 617 plus distance 618.

FIG. 7 shows another embodiment of a low profile sensor 700. In thisembodiment, signal trenches can be replaced by shaped features disposedon the edge of the substrate. Substrate 702 includes pad 106 disposed ona first side of substrate 702. Shaped feature 706 can be formed on onecorner of substrate 702. Metal layer 704 can be disposed on pad 106 andcan also be disposed on shaped feature 706. Wire bond ball 604 can bepositioned on shaped feature 706 such that wire 708 can be maintainedbelow surface plane 220 of sensor 104.

FIG. 8 shows a side view 800 of one embodiment of a way of formingmultiple low profile sensors. Multiple low profile sensors can be formedon a silicon wafer with each individual low profile sensor formed on anindividual die on the wafer. Prior to separating the individual dice, agrinding wheel 802 or shaped saw blade can form signal trenches 215across two or more dice, with a relatively continuous grind or cut. Inthe example shown in FIG. 8, grinding wheel 802 can form signal trenches215 in first and second low profile sensors 805 and 807 respectively. Ina later operation, a saw can separate the dice forming a saw cut 810.

FIG. 9 illustrates optional features that can be applied to a lowprofile sensor assembly 901 embedded in a PCB 204. The low profilesensor assembly 901 can include sensor 104 and substrate 102. After thelow profile sensor assembly 901 is embedded in PCB 204, empty voids 902,especially in the areas of signal trench 215, can be filled with anepoxy, resin or other like material to strengthen the bond between lowprofile sensor assembly 901 and PCB 204 and form a relatively planarsurface. In another embodiment, components 904 can be disposed on PCB204, on the side facing away from sensor 104. Components 904 can bepassive components such as resistors, inductors, capacitors or the like.Components 904 can be coupled to sensor 104 or other devices.

FIGS. 10A and 10B illustrate another embodiment of a low profile sensor1000. In this embodiment, individual signal trenches can be replacedwith a single trench 1010 that can be formed on edge of substrate 102.Sensor 104 can be disposed on one surface of substrate 102. Pad 106 canbe disposed on the same planar surface as sensor 104. Metal layer 1015can couple pad 106 to at least one region of single trench 1010. Inanother embodiment, pads can be positioned within single trench 1010region as shown with pad 1020. Metal layer 1025 can be deposited overpad 1020 and be positioned in single trench 1010. FIG. 10B shows a sideview of low profile sensor 1000. Metal layer 1015 can be deposited onpad 106 and into single trench 1010. In another embodiment, pad 1020 canbe positioned in single trench 1010. Metal layer 1025 can be depositedon pad 1020 and into single trench 1010.

FIGS. 11A-11E illustrate steps that can be used to mount a low profilesensor on a substrate. In one embodiment, the substrate can be a thinsubstrate 1110, such as a flexible cable. FIG. 11A shows an initialstate of thin substrate 1110 and pads 1120. Adhesive 1130 can bedeposited on thin substrate 1110. Adhesive 1130 can be an epoxy, glue,adhesive tape or other similar article. In FIG. 11B, substrate 1140including sensor 1145 can be positioned on adhesive 1130. In FIG. 11C,wire bond balls 1150 can be attached to substrate 1140 in preparationfor bond wire attachment. In FIG. 11D, bond wires 1160 can be attachedto wire bond balls 1150 and can couple signals from sensor 1145 to pad1120. In one embodiment, optional wire bond balls 1165 can be coupled topad 1120. In FIG. 11E bond wires 1160 can be encapsulated to protectthem in an epoxy 1170, resin or similar material.

FIG. 12 is a flowchart 1200 of method steps for mounting a low profilesensor on a substrate. In one embodiment, the substrate can be a thinsubstrate such as a flexible circuit. The method begins in step 1210where an adhesive is applied to a substrate. The adhesive can be aliquid adhesive such as an epoxy or can be a tape based adhesive. Instep 1220, the sensor/substrate combination can be bonded to thesubstrate. In step 1230, bond wire balls can be attached to thesubstrate. In one embodiment, the bond wire balls can be coupled tometal layers on the substrate enabling access to the signals in thesensor. In step 1240, bond wires can be attached to bond wire balls andpads disposed on the substrate. In step 1250, bond wires can beencapsulated. Encapsulation can help protect fragile bond wires fromdamage.

FIG. 13 is a top view of yet another embodiment of a low profile sensor1300. This embodiment can include both individual single trenches asdescribed in FIG. 1 and multiple signal trenches that can include morethan one signal as described in FIG. 10. Low profile sensor 1300 caninclude substrate 102 and sensor 104. Pads 106 can be disposed outsideof a trench. For example, pad 106 is disposed beyond multiple signaltrench 1310 and beyond single signal trench 1311. In another embodiment,the pad can be disposed inside the trench region. For example, pad 1020can be disposed within multiple signal trench 1310 or within singletrench 1311. Metal layers 1015 can couple to pads 106 beyond signaltrenches 1310 and 1311. Alternatively, metal layers 1025 can couple topads 1020 within signal trenches 1310 and 1311. In some embodiments,multiple signal trenches 1310 can provide greater signal densities,while in some embodiments, single signal trenches 1311 can providegreater strength to substrate 102. Low profile sensor 1300 can possessadvantages of both the signal and multiple signal trench systems.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination.Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer readable code ona computer readable medium for controlling manufacturing operations oras computer readable code on a computer readable medium for controllinga manufacturing line. The computer readable medium is any data storagedevice that can store data which can thereafter be read by a computersystem. Examples of the computer readable medium include read-onlymemory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, andoptical data storage devices. The computer readable medium can also bedistributed over network-coupled computer systems so that the computerreadable code is stored and executed in a distributed fashion.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of specific embodimentsare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the described embodiments to theprecise forms disclosed. It will be apparent to one of ordinary skill inthe art that many modifications and variations are possible in view ofthe above teachings.

What is claimed is:
 1. A sensor assembly suitable for receiving a touchinput, the sensor assembly comprising: a sensor having a first surfaceconfigured to receive the touch input; a substrate that supports thesensor at a second surface that comprises an extended portion thatextends away from the sensor; and a conductive pad disposed on theextended portion of the substrate, the conductive pad electricallycoupled with the sensor, wherein the conductive pad is electricallycoupled to an external circuit by an electrically conductive materialthat lies within a region bounded by a reference plane coplanar with thefirst surface.
 2. The sensor assembly of claim 1, wherein the externalcircuit comprises a printed circuit board (PCB) having an opening havinga size and shape suitable for accommodating the substrate and thesensor, and wherein the PCB further comprises an exterior surfacegenerally coplanar with both the reference plane and the first surfaceand an interior surface at least some of which is used to support thesensor.
 3. The sensor assembly of claim 2, wherein the PCB includes asecond conductive pad electrically coupled to the sensor via theelectrically conductive material.
 4. The sensor assembly of claim 3,wherein the second conductive pad is electrically coupled to theelectrically conductive material at a trench portion of the substratecorresponding to a material removal region.
 5. The sensor assembly ofclaim 4, wherein the electrically conductive material carries anelectrical signal associated with the touch input from the sensor to thePCB.
 6. The sensor of claim 4, wherein the material removal regioncomprises a signal trench having a profile selected from a groupconsisting of a ramp profile, a vertical profile, a curved profile, anda bowl shaped profile.
 7. The sensor of claim 2, wherein the substrateand the conductive pad are bounded between the reference plane and theinterior surface of the PCB.
 8. A sensor assembly, comprising: asubstrate including a first trench region and a second trench region,the substrate further including a first surface surrounded by the firsttrench region and the second trench region; a sensor located on thefirst surface, the sensor configured to detect a touch input eventassociated with a contact to the sensor; and a conductive pad disposedbetween the sensor and the first trench region, the conductive padelectrically connected with the sensor and the substrate.
 9. The sensorassembly of claim 8, further comprising a first electrically conductivematerial electrically coupled with the conductive pad.
 10. The sensorassembly of claim 9, further comprising a second electrically conductivematerial electrically coupled with a second pad disposed in the secondtrench region.
 11. The sensor assembly of claim 10, wherein the firstelectrically conductive material extends to the first trench region, andwherein the second electrically conductive material extends to thesecond trench region.
 12. The sensor assembly of claim 11, wherein thesensor comprises a touch input surface that receives the touch inputevent, and wherein the substrate, the first electrically conductivematerial, and the second electrically conductive material are bounded bya plane extending from the touch input surface.
 13. The sensor assemblyof claim 9, further comprising a printed circuit board (PCB) having anopening that receives the substrate.
 14. The sensor assembly of claim13, wherein the sensor further comprises a touch input surface, andwherein the substrate and the first electrically conductive material arebounded between the PCB and a plane extending from the touch inputsurface.
 15. A sensor assembly suitable for use with a touch input, thesensor assembly comprising: a substrate comprising a surface and atrench region that is sub-flush with respect to the surface; a sensordisposed on the surface and electrically connected with the substrate,the sensor having touch input surface configured to detect the touchinput; a conductive pad disposed on the surface, the conductive padelectrically coupled with the sensor and the substrate; an electricallyconductive material extending from the conductive pad to a secondconductive pad external with respect to the substrate; and a printedcircuit board (PCB) including an opening that receives the substrate,wherein PCB, the substrate, and the electrically conductive material aresub-flush with respect to the touch input surface.
 16. The sensorassembly of claim 15, wherein the second conductive pad is disposed onand electrically connected to the PCB.
 17. The sensor assembly of claim15, wherein the second conductive pad is disposed on and electricallyconnected to a separated device embedded in the PCB.
 18. The sensorassembly of claim 15, further comprising an electrical componentdisposed on an exterior surface of the PCB and configured to receive anelectrical current.
 19. The sensor assembly of claim 15, wherein theelectrically conductive material comprises a first electricallyconductive portion and a second electrically conductive portionelectrically coupled with the first electrically conductive portion at alocation associated with the trench region.
 20. The sensor assembly ofclaim 15, wherein the substrate further comprises a second trench regionopposite the trench region, and wherein the second trench regioncomprises a third conductive pad.